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Developing antibacterial nanocoatings for textiles in health care
Martin Bennink1, Henk Gooijer2, Ger Brinks2
1 NanoBio research group 2 Smart Functional Materials research group
Saxion University of Applied Sciences, Enschede, The Netherlands
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Contents
- Bacterial infections in health care (the problem)
- Goal of this project Synthesis of
nanomaterials
Application to textile
Testing antibacterial
property
Assessing toxicity
Abrasion by wear and washing
Implemen-tation in practice
- Conclusions and what’s next - Acknowledgements
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The problem
- Bacterial infections are one of the most important challenges hospitals and other health care institutions are faced with.
- The chance of acquiring an infections with an hospital within the Netherlands is about 5.5 % (RIVM report 2014).
- Additional costs per year related with these bacterial infections is 136 M€ (in the Netherlands)
- Contamination occurs during transfer via personnel and is enhanced by bacteria growing in wounds of patients.
Medisch Spectrum Twente, Enschede
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Goal of the project
Develop and apply a coating with nanomaterials on the textile that reduces the growth of bacteria.
Focus is on: - Doctor’s uniform - Separation curtains - Surgery jacket Doctor’s uniform
Washing cloth
Bed and cushion sheets
Separation curtains
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Bacteria in textiles
Textiles Apparels, clothing
Home textiles (mattresses, floor coverings, show linings)
Outdoor textiles
Textiles provide an excellent environment, because of their:
- Large surface area
- Ability to retain moisture
- Additives which are a source of nutrition for bacteria (lubricants, antistatics, …)
(Natural textiles are more prone to be infected with bacteria than synthetic one)
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Survey of compounds
EU regulations
Charge Water solubility
Application Antibacterial mechanism
Toxicity
Silver Biocidal product regulation
Cation 80% insoluble
Medicine, industry and home use
Cell are lysed Genotoxic, cytotoxic,
Titanium dioxide
Biocidal product regulation
Anion Not soluble
UV-protection in cremes and coatings
UV activated TiO2 forms radi-cals that oxidize organic materials
Carcinogenic when inhaled, toxic for aquatic life
Zink oxide Biocidal product regulation
Anion Not soluble in water
UV-protection and pigment (in plastics, ceramics)
Reacts with enzymes and forms radicals
Toxic for aquatic life, when inhaled damage to togans, allergan
Phosphotungstic acid hydrate
REACH Anion Soluble in water
Antibacterial, antitumoral, antiviral appls
Oxidizes organic materials
Irritant for eyes and lungs (when inhaled)
Silicotungstic acid
REACH Anion Soluble in water
Antibacterial, antitumoral, antiviral appls
Oxidizes organic materials
Irritant for eyes and lungs (when inhaled)
Triclosan Biocidal product regulation
Anion Not soluble in water
Desinfectant Biocide with multiple biological targets
Allergant, produces water dioxines. Toxic for aquatic life
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Antibacterial nanoparticles coatings
Nano-silver Antibacterial properties
Refridgerators Sport socks Wound dressing
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Antibacterial socks
Sport socks
1-5 out of 100 fibrils is darker (Ag coated)
Only the bottom part of the sock was found to contain Ag-containing fibers.
Ag is present as a continuous layer of thickness 100-200 nm (EDX)
From: Report “Nanoparticles in consumer products”, RIVM
BUT: Nanosilver is very difficult to firmly attach to
textiles and has been shown to be harmful for aquatic environment.
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Survey of compounds
EU regulations
Charge Water solubility
Application Antibacterial mechanism
Toxicity
Silver Biocidal product regulation
Cation 80% insoluble
Medicine, industry and home use
Cell are lysed Genotoxic, cytotoxic,
Titanium dioxide
Biocidal product regulation
Anion Not soluble
UV-protection in cremes and coatings
UV activated TiO2 forms radi-cals that oxidize organic materials
Carcinogenic when inhaled, toxic for aquatic life
Zink oxide Biocidal product regulation
Anion Not soluble in water
UV-protection and pigment (in plastics, ceramics)
Reacts with enzymes and forms radicals
Toxic for aquatic life, when inhaled damage to togans, allergan
Phosphotungstic acid hydrate
REACH Anion Soluble in water
Antibacterial, antitumoral, antiviral appls
Oxidizes organic materials
Irritant for eyes and lungs (when inhaled)
Silicotungstic acid
REACH Anion Soluble in water
Antibacterial, antitumoral, antiviral appls
Oxidizes organic materials
Irritant for eyes and lungs (when inhaled)
Triclosan Biocidal product regulation
Anion Not soluble in water
Desinfectant Biocide with multiple biological targets
Allergant, produces water dioxines. Toxic for aquatic life
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Polyoxometalates
- Polyoxometalates (POMs) are discrete anions of early transition oxides, such as molybdenum (Mo), tungsten (W) and vanadium (V) oxides.
- They can have a variety of structures
- In this project we use the following two polyoxotungstates:
Phosphotungstic acid
Si
Silicotungstic acid
SiW12O40 PW12O40
Polymeric oxoanions, that form a 3D network, around Si or P
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Synthesis of silicotungstic acid
12 Na2WO4 2 H2O + Na2SiO3 + 26 HCl
H4SiW12O40 (x)H2O + (13-x)H2O + 26NaCl
Si
Silicotungstic acid
End product
(82% yield)
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AFM characterization
Silicotungstic acid
Deposited on mica
Imaged in tapping mode
0.7 nm
Monolayer of POMs
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SEM characterization
Crystallinity of the material is clearly visible
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Applying the POMs to textile
For health care applications, mostly used textiles are:
- Cotton (100%)
- Polyester (100%)
- Blend cotton/polyester (35%/65%)
(standard test cloths are used to overcome fluctuations in textile quality)
CHALLENGE:
To apply the nanomaterial such that it is durable and can withstand washing cycles.
Vanderwaals interaction Ionic interaction
Textile needs be cationized (cotton is negatively charged, polyester is neutral)
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Application methods
Foulard process:
allows thorough impregnation, no affinity with textile required
Extrusion process:
allows thorough impregnation, affinity with textile is required
Inkjet printing:
allows local application, no affinity required
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Application methods
Foulard process:
allows thorough impregnation, no affinity with textile required
Extrusion process:
allows thorough impregnation, affinity with textile is required
Inkjet printing:
allows local application (one-sided), no affinity required
- Ink prepared from 1 and 2% nanomaterials was too viscous.
- Printheads got clogged - Applying
nanomaterials through spraying
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Application methods
Foulard process:
allows thorough impregnation, no affinity with textile required
Extrusion process:
allows thorough impregnation, affinity with textile is required
Inkjet printing:
allows local application, no affinity required
- No control over concentration that is applied to the textile, dependent on affinity of the POM to the textile surface
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Application methods
Foulard process:
allows thorough impregnation, no affinity with textile required
Extrusion process:
allows thorough impregnation, affinity with textile is required
Inkjet printing:
allows local application, no affinity required
- Accurate control over amount of nanomaterials applied. Fluid pick-up after impregnation is constant.
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Quantifying amount of nano-material on textile (SEM/EDS)
EDS = energy-dispersive X-ray spectroscopy
Si
Si
W
Cotton treated with 2% Silicotungstic acid (padding with Foulard)
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Quantifying antibacterial activity
(1-3 105 CFU/ml)
Method
(1-3 108 CFU/ml)
Definition antibacterial activity
t=0 and t=24h
C : control textile
T : treated textile
A < 2: not antibacterial
A = 2-3 significant inhibition
A > 3: strong inhibition
We aim for A > 3 (i.e. more then 1000 fold reduction in growth rate)
Textile is pressed against agar surface for a certain time using standard weight to transfer the bacteria 200 L
Is added to the textile diluted
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Antibacterial activity
- Both cotton and blend show strong inhibition (A>3) with 1 and 2%.
- PET appears to show no difference
0
2
4
6
8
10
12
1% 2%
An
tib
acte
rial
act
ivit
y A
POM %
Cotton phospho
Blend phospho
PET phospho
Cotton tungsto
Blend tungsto
PET tungsto
against Klebsiella pneumonia
(Gram negative)
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Antibacterial activity
0
2
4
6
8
10
12
1% 2%
An
tib
acte
rial
act
ivit
y A
POM %
Cotton phospho
Blend phospho
PET phospho
Cotton tungsto
Blend tungsto
PET tungsto
against Staphylococcus aureus (Gram positive)
- Both cotton and blend at 1% show not sufficient antibacterial effect.
- At 2% the blend and cotton with silicotungstic acid are sufficient.
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Toxicity of nanomaterials
The nanomaterials are supposed to kill bacteria (bactericidal) or reduce the growth of bacteria (bacteriostatic).
But how do cells respond to the nanomaterials ???
Cytotoxicity to POMs in solution
Cytotoxicity to POM coated textile
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Cytotoxicity of POMs in solution
Si
Morphology of MDA-MB-231 cells as a function of concentration of POM:
Cell shape changes and more aggregation is observed
Quantification of this is done with AlamarBlue test (LD50).
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Cytotoxicity of POMs in solution
Si
Silicotungstic acid
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Cytotoxicity of POMs in solution
Phosphotungstic acid
3T3 cells show very similar results
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Cytotoxicity of treated textile
(is work in progress)
- Main challenge here is to find a good protocol (How do you press the textile onto the cell culture)
- Some results do not show a decrease in % of living cells as concentration increases and results turn out to be not so reproducible.
- Cell appear to stick to the textile, making it difficult to get reliable data.
- Transwell experiments in which the textile is below the membrane, does not result in any toxicity, but how representative is this experiment.
More work needs to be done here
And how representative are these cell lines for the skin ?
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Effect on skin flora
Skin is your largest organ (surface is 1.8 m2, mass 10 kg) Skin flora = micro-organisms that live on the skin (transient and resident skin flora) Question is whether the antimicrobial activitity of the nanomaterial on S. epidermis and P. acnes is the same as for the pathogenic bacteria. P. Elsner, "Antimicriobials and the Skin Pysiological and Pathological Flora," Current Problems in Dermatology, vol. 33, pp. 35-41, 2006
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Abrasion of nanomaterial
Abrasion of the nanomaterial is measured using a “crock”-device. The textile is worn against a test sample using standard conditions. (ISO 105X12) Then we use SEM/EDS to determine how much nanomaterial is transferred
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Abrasion of nanomaterial
Example of 1% phosphotungstic acid on cotton in dry conditions
Not detectable
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Abrasion of nanomaterial
W Dry conditions (% mass)
W Wet conditions (% mass)
Cotton 1% Phospho Non detectable Non detectable
Cotton 1% Silicic Non detectable Non detectable
Cotton 2% Phospho Non detectable Non detectable
Cotton 2% Silicic Non detectable 0,99
Blend 1% Phospho Non detectable 0,58
Blend 1% Silicic 0,09 1,55
Blend 1% Phospho Non detectable 1,48
Blend 1% Silicic Non detectable Non detectable
PET 1% Phospho 0,72 Non detectable
PET 1% Silicic Non detectable Non detectable
PET 1% Phospho Non detectable Non detectable
PET 1% Silicic 1,11 Non detectable
Amount of abrasion is low
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Abrasion by washing
Textiles in healthcare are washed very often and therefore the abrasion by washing is investigated (95 C)
Most of the nanomaterial appears to be removed from the textile !
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Conclusions
- POMs can be synthesized in large quantities.
- Using various methods we can apply these POMs to textile materials
- Strong antibacterial activity of silicotungstic acid (1% and 2%) on cotton and blend.
- LD50 values are 0.2 to 0.5% for POMs in solution.
- Abrasion by friction is minimal.
- Washing at 95 C removes most of the nanomaterials from the textile.
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What still needs to be done
Next steps:
- Test abrasion by washing at other washing conditions.
- Repeat the toxicity studies on cells, but also apply this to a skin model system (is ongoing right now)
- Measure toxicity of the treated textiles directly (not that of free POMs)
- Rethink the strategy of attaching the POMs (but if they are immobilized, this might affect the antibacterial effect of the textile).
- Study the effect on the skin flora
- Consider other application fields (floor coverings).
More work needs to be done here
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Nanostructured surfaces
Bio-inspired nanostructured surfaces Antibacterial properties
Dragonfly
Ivanova et al., Nature Communications 4: 2838 (2013)
SEM image of forewing (scale bar = 200 nm)
Can we create a similar structure onto textile fibers ?
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Acknowledgements
Nicole Zeijen Rick Hobert Ger Brinks Henk Gooijer Paul Borm Johan Molling Hasan Mashhadani Michelle Lukas Robin Verwijs Erwin Nijhuis
RAAK-mkb grant
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Thank you
Martin Bennink
Lector NanoBio Saxion University of Applied Sciences Enschede, NL
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Other activities in NanoBio …
Textiles in health care (SIA, RAAK-MKB)
Antibacterial nanostructured surfaces
(TFF) “Nano meets forensics” (TFF)
Heart-on-a-Chip (SIA, RAAK-MKB)
in preparation
Labelfree sensing of small proteins (insulin)
(TFF)